Topic: Oil pressure sending unit


pinnsky    -- 05-26-2019 @ 3:21 PM
  I have a 59ab in my 36. What is the correct sending unit for this engine?
60# or 80#.
Thanks, Tom


51woodie    -- 05-26-2019 @ 7:40 PM
  The Dennis Carpenter catalogue shows the 35-42 oil pressure sending unit is a 50lb unit, P/N 48-9278 for $49.95
Mac's lists the sending unit for 35-42 as a 60lb unit, P/N 48-9278 for $53.99 Drake only shows sending units for 1944 to 53, all at 80lbs.


40cpe    -- 05-26-2019 @ 7:52 PM
  If you are still using the original dash gauge in your '36, I would think you should use a sending unit calibrated to the gauge and not worry about the model of the engine.


51woodie    -- 05-27-2019 @ 2:28 AM
  Now this is a puzzle. I agree with 40cpe, that it makes sense that the sender/gauge should match. I have a 80lb sensor on my 59ab in my '46, and road speed with 15-40 oil gives me close to 60psi on the mechanical gauge, and just over half needle on the dash gauge. My best guess would be the 60lb unit, but then I think there are post on this site that says the difference between 60 vs 80 doesn't make a big difference. My bet is there is someone on the Forum that has the right answer.


40 Coupe    -- 05-27-2019 @ 4:21 AM
  The sending unit matches the engine oil pump. I believe the 59AB uses the higher pressure pump so use the 80# sending unit.


len47merc    -- 05-27-2019 @ 6:14 AM
  If it is a STOCK '46-'48 59ab 60 lb would be correct for the engine but not the car. 'High precision' (joking) original gauges should read for that engine around 30 to 35 PSI on 10-30 oil when hot at RPM and as low as 5 PSI or maybe even a tad lower at idle, again when hot. That would be considered 'normal'. The stock/original oil pump on a 59ab will not produce 60 PSI pressure in a brand new engine even with 20/50 oil on a stock gauge and even if it did once warm to hot it would fall back to the 30 to 40 PSI range at RPM at most. If you want accuracy put in a mechanical gauge. If you want originality stick with your stock gauge and if you've got oil pressure that's all you need to be concerned about - these engines were designed to run with very low to modest oil pressures.

Steve

This message was edited by len47merc on 5-27-19 @ 6:14 AM


TomO    -- 05-27-2019 @ 7:23 AM
  Originally the 35-42 engines had a 50# (48-9278) sending unit and pressure relief valve. 46-53 engines used an 80# (41A-9278) sending unit.

The sending unit, oil pump and pressure relief valve should match. The 50# gauge will read 5/8 lower (read 50# at 80#, at a reading of 15# with an 80# sending unit you will have 24# of oil pressure) than the real oil pressure with the 80# sending unit.

To answer pinnsky original question, the sending unit should match the oil pump and pressure relief valve. The engine most likely has an 80# pump and pressure relief valve.

I don't know what is inside the replacement sending units, so I would look for a King-Seely unit with KS stamped on the top and 80 stamped on the pipe thread brass fitting. My Lincoln had a replacement unit and the gauge never worked well with it, it finally failed this Spring and is going to be replaced by a good used King-Seely unit.

Tom

This message was edited by TomO on 5-27-19 @ 7:33 AM


pinnsky    -- 05-27-2019 @ 10:00 AM
  Thanks gentlemen, 80# it is.


51woodie    -- 05-27-2019 @ 11:25 AM
  The 59ab in my '46 Super Deluxe was obviously rebuilt at one time, as it has adjustable lifters, and what must be an 80lb pump. I use Rotella 15-40 (see dipstick) and the attached pics tell the story on the pressures I have. An 80lb sender feeds the dash gauge, and the dash gauge reads lower than the mechanical gauge. As someone said, "If it has any pressure showing, don't worry about it".


40cpe    -- 05-27-2019 @ 6:42 PM
  I won't belabor the point but want to emphasize again that the sending unit and gauge are synchronized with each other. If you want somewhat accurate reading they must match. I fail to understand what effect the sending unit has on the oil pump and the relief spring. An 80# pump might peg a 50# gauge and sending unit, but if you want the gauge calibrated as Ford built it you should use a matching sending unit, IMHO.

Here is an old Fordbarn thread with testimonials of some who have used mis-matched senders/gauges.
https://fordbarn.com/forum/showthread.php?t=153334


len47merc    -- 05-28-2019 @ 4:15 AM
  Well stated 40cpe and much clearer than my response above. I also want to correct my response above in that for '46-'48 an 80# sending unit is correct as the pump, sending unit and lastly the gauge, for these years specifically, are designed and rated to produce, sense and 'measure' up to 80#. My eyesight and memory were a bit off there as from memory I correctly recalled the visual mid-point of my '47's gauge as being at 30 lb and then incorrectly doubled it to produce an assumed result of 60# versus factual. The gauge does read '0-30-80'.

I'll stand on the balance of my earlier reply and agree with everyone's comments. Also should've pulled out my parts catalogs to confirm my eyesight and memory!

Steve


TomO    -- 05-28-2019 @ 6:54 AM
  With a 50# sending unit and an 80# oil pump and pressure relief valve, my Merc had the gauge pegged at any speed above 35 MPH. With an 80# sending unit, the gauge reads from just below the center, to above the center with 10w-30 oil. IMHO having a pegged meter is not very helpful and if I want to know the exact pressure, I can do a little arithmetic.

I test the sending units with my air compressor that has an accurate pressure regulator and a spare dash unit. The units stamped with KS are usually accurate.

Tom


40cpe    -- 05-28-2019 @ 10:11 AM
  That is a helpful explanation Tom. The original poster is going into it equipped to make his own decision now.


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